Heat and Thermodynamics 5 Question 26
27. When an ideal diatomic gas is heated at constant pressure the fraction of the heat energy supplied which increases the internal energy of the gas is
(1990, 2M)
(a) $\frac{2}{5}$
(b) $\frac{3}{5}$
(c) $\frac{3}{7}$
(d) $\frac{5}{7}$
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Solution:
- The desired fraction is
$f=\frac{\Delta U}{\Delta Q}=\frac{n C _V \Delta T}{n C _p \Delta T}=\frac{C _V}{C _p}=\frac{1}{\gamma}$ or $f=\frac{5}{7} \quad\left(\right.$ as $\left.\gamma=\frac{7}{5}\right)$
